Electric motors are well known to produce heat during their operation. Usually the amount of heat produced increases with the increasing horsepower of the electric motor. This heat causes break down of the insulation of the wiring, reduces the efficiency of the motor, causes deterioration of non-metallic components such as seals and can produce premature failure of metallic parts of the motor. The heat generated by the electric motor may even adversely effect things in the immediate vicinity of the motor. As the demand grows for higher horsepower electric motors in such applications as machine tools, the problem of heat dissipation increases. The problem of removing heat from electric motors has been previously attacked in a variety of ways. For example fins have been used on motor casings to dissipate heat, fans have been incorporated inside electric motors for air cooling and air circulation patterns of numerous designs inside electric motors have been proposed and used. Liquid e.g. oil cooling of electric motors is known. Where liquid cooling of an electric motor has been used, the motor has been provided with a heat exchange jacket having passageways for the circulation of the liquid through the jacket. Although many of such passageway geometries are effective for cooling the electric motor, they are difficult and costly to produce. Thus, they often add significant cost to the motor.
For electric motors that are both relatively small in size and high in horsepower the removal of heat is a particularly important problem, especially when trying to maintain the small size of the motor. The problem of heat removal in a small, high horsepower electric motor is aggravated by totally enclosing the motor to protect it from various components of the environment in which it is operated, e.g. in machine tools. Such relatively small, high horsepower electric motors equipped with a close fitting ccooling jacket having a spiral fluid passageway for conducting a cooling fluid (e.g. oil or water) are known and have been used in machine tools made by Cincinnati Milacron Inc. The fluid flow path in the spiral passageway gradually and continuously changes direction producing little or no turbulent flow of the fluid, and thus reduced cooling efficiency. Further, producing the spiral passageway in the jacket is difficult and costly. It is, therefore, desirable to provide a fluid flow path geometry that produces turbulent fluid flow, that is easy to produce and is of low cost, in a heat exchange jacket for an electric motor.
It is an object of this invention to provide a heat exchange apparatus for cooling an electric motor, including a fluid flow path geometry producing turbulent fluid flow. A further object of this invention is to provide an electric motor having a fluid flow passageway geometry producing turbulent flow of a heat exchange fluid to improve heat dissipation from the motor.